In several industries, and in particular the food industry, there is a need to separate liquid greases, fats and oils from waste water prior to passing the water to the sewage system. The waste water could be, for example, discharged from a washing device for cleaning dinnerware and cooking utensils. If the greases and fats solidify in the sewage system, a blockage can occur which is expensive to remediate.
Additionally, there is a movement in many localities to recycle grease and oils.
A commercially available separation device of the type described in European Patent EP 890381 B1 is shown generally in FIGS. 1a and 1b. FIG. 1a illustrates an exterior perspective view of the separation device 10. Effluent (containing two or more immiscible liquids of different densities, typically water entrained with oil, grease dissolved fats and other particles) is received at inlet 12 providing a passage into housing 14 (including removable lid 15). Effluent is heated using a probe-type heater 16, which is coupled to an electrical connection. As described below, the immiscible liquids separate within housing 14, and the less dense material (e.g., grease and oils) empties into container 18. The more dense liquid (e.g., water) is discharged from water outlet 20. Silt may accumulate at the bottom of housing 14. The silt may be periodically discharged through silt outlet 22.
Operation of the separation device 10 is described in greater detail in connection with FIG. 1b (as well as EP 890381 B1, which is incorporated by reference). FIG. 1b illustrates a cross-sectional side view of the separation device 10. A coarse filtration chamber 24 is defined between the housing 14 and control plate 25, which extends the full width of the housing. As effluent enters the coarse filtration chamber 24 through inlet 12, it passes through a filtering basket 26, which filters out solid particles, such as undissolved fat and other food particles.
After passing through the basket 26, the effluent enters the separation chamber 28, defined by control plate (baffle) 25, control plate (baffle) 30 (which extends the full width of the housing), top plate 32 and the bottom of housing 14. There are two exits from the separation chamber: (1) through floating ball valve 34 and (2) through passage 36, disposed between the bottom of control plate 30 and the bottom of the housing 14. Top plate 32 is angled upward from the bottom portion of control plate 25 towards control plate 30.
Weir plate 38, which extends the full width of the housing, defines a water (high density liquid) release chamber 40, along with control plate 30 and the housing 14. Outlet 20 is disposed through the housing.
In operation, as the effluent enters the separation chamber 28, the lower density liquid (grease/oil) rises. The flow through the separation chamber 28 is set at a rate that allows the lower density liquid to separate from the water and float upwards to the surface of the water, where it is contained below the sloping top plate 32.
The sloping top plate 32 forces the lower density liquid to accumulate at the entry to floating ball valve 34. Floating ball valve 34 is shown in greater detail in connection with FIG. 2. Floating ball valve 34 uses a ball that floats at the interface between the high density liquid and the low density liquid. When the high density liquid reaches a predetermined height, the ball rises to a height which stops flow from the separation chamber 28 to the container 18.
As the water flows through the separator 10, it must rise above the top of weir 38 in order to exit. Accordingly, the water in separation chamber 28 attempts to rise to approximately the same height. Since the top of the separation chamber 28 is below the top of weir plate 38, the hydrostatic pressure of the upward force of the water will push the separated grease/oil at the top of the separation chamber 28 through valve 34. The water, however, cannot pass through the valve 34, because the floating valve will stop its passage. Hence, once all the separated grease/oil is forced out of the separation chamber, the valve will remain closed until more grease/oil accumulates.
The separated water passes through passage 36, over weir plate 38 and out outlet 20. Silt in the water tends to accumulate at the bottom of housing 14, unable to rise over weir plate 38. Silt valve 22, located at the bottom of housing 14, can be opened periodically, and the flow of water out of the valve will flush out the silt.
This separator, along with other existing separators, operates based on very specific levels of the waste water inlet, water outlet and byproduct outlet. The valve 34 is an effective mechanism for preventing water from entering the removable tank; otherwise water would mix with the grease/oil in the tank 18 and quickly fill the removable tank. Usually, the valve 34 includes a ball which rises and falls at the boundary of the separated fluids. While the ball is reliable in blocking water from getting into the tank 18, it is not reliable in releasing once the water level has dropped below a safe level. Often, the ball will stick in a closed position due to one of the fluids preventing the oil/grease from entering the removable tank 18 as well as the water.
In many fields of use for the separator 10, and in particular the food industry, it can be assumed that the employees who will operate and maintain the separator will be relatively transient between employers. Accordingly, aspects of the operation and maintenance of the separator must allow for unfamiliarity with details. Matters such as periodic cleaning of various components of the separator, such as the floating ball valve, if performed incorrectly, can lead to unwanted consequences, such as allowing water to exit into the oil/grease container or oil/grease flowing out of the outlet 20. Further, a backsplash of grease may occur when cleaning the valve, which can result in both the employee and the surrounding area to be soiled with grease.
Some alternatives to a valve such as this are set forth in U.S. Pat. No. 7,297,284, which is incorporated by reference herein. The valves shown in the patent either ameliorate factors which cause sticking, or eliminate sticking through electromechanical assist; however, these valves are typically more complicated and much more expensive than the ball valve.
Therefore, a need has arisen for a separator that operates without valve mechanisms which can stick in a set position.